Doubt regarding Types

[Karthik Kumar]

Hi All, 
 I  was trying to write go program in haskell - My code fragment looks
like this - 

<---- > 
getBoardSize :: IO Bool 
-- TODO : What could be the type of getBoardSize 
getBoardSize  = do c <- getLine
                   validateBoardSize ( atoi c ) 

-- Convert a string to an integer.
-- This works perfectly fine. 
atoi          :: [Char] -> Int
atoi (h : []) = if isDigit h then digitToInt h else 0
atoi (h : t) =  if isDigit h then digitToInt h * ( 10 ^ length t) +
atoi t else 0

-- validateBoardSize
-- To validate the board size
validateBoardSize   :: Int -> Bool
validateBoardSize d = (d == 9 || d == 13 || d == 19 ) 

<----> 


ERROR "test1.hs":21 - Type error in final generator
*** Term           : validateBoardSize (atoi c)
*** Type           : Bool
*** Does not match : IO a

Actually i guess there is something wrong with the type mentioned for
getBoardSize function , but am clueless abt this. 

  Thanks in advance for your help in this regard.

Cheers
Karthik


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